The video embedded above is entitled "Chattel Slavery & How the UK Redeemed Humanity" and produced by Black Pigeon Speaks. Essentially, the video is about how the UK, via the power and authority it held when it was a world-wide empire, was able to largely end chattel slavery throughout most of the world. And let's not forget the wealth: Britain set aside a significant portion of its national wealth to compensate slave owners forced to give up their slaves.
The hold outs were, as would be expected, among Muslim countries in Africa and the Middle-East. (As one blogger notes, "[Saudi Arabia] is a modern country, they abolished slavery in 1967, but old expats have reported seeing slave auctions as late as 1981"). The United States, contrary to what liberals would have you believe, played a very minor role in the slave trade: "of the 11.2 million slaves imported from Africa in the slave trade, only 4% of them, or 450,000 arrived in the United States." And, of course, beginning in 1808, it was illegal to import new slaves into the United States.
Of course, the trail of the African slave trade begins with the wars and raids by African tribes upon each other. The Daily Mail has an article entitled "The slave repellant: Unique images show 'deformed' Ethiopian tribeswomen who wear colourful accessories and lip plates that evolved to avoid being selected as slaves." (See photograph below)
As the article notes, "although their appearance is striking, their traditional dress dates back to the slave era, where women believed fitting lip plates would make them less attractive to slave owners."
In the absence of European rule, the slave trade flourishes once again. "More than 45 million men, women and children globally are trapped in modern slavery." As for Africa, "[t]he most recent Global Slavery Index, published in November, 2014, put the total number of slaves on the African continent at 6.4 million, including 5.6 million in Sub-Saharan Africa and an additional 800,000 in the northern region, including Morocco, Algeria, Tunisia, Libya and Egypt." And in India, once the crown jewel of the British Empire, "18 million people, or 1.4% of the population" are slaves. "Behind India was China (3.39 million), Pakistan (2.13 million), Bangladesh (1.53 million) and Uzbekistan (1.23 million)."